Injection co-molding with offset parting line

ABSTRACT

Method for insert molding film covered plastic parts are disclosed that facilitate wrapping of the paint film around edges of the part A mold cavity ( 210 ) is provided wherein the requisite edge extremities ( 212, 214 ) of the cavity ( 210 ) are provided in an offset or spaced relation to the mold parting line plane ( 216 ). Location of the mold extremities at this position helps to secure the paint film in the mold cavity ( 210 ) and prevents pinching of the film that would otherwise occur along the mold parting line ( 216 ).

FIELD OF THE INVENTION

[0001] The present invention pertains to improved methods of insertmolding a laminated film or the like over a plastic substrate and to thefused film—plastic parts made thereby.

BACKGROUND OF THE INVENTION

[0002] A variety of injection molded parts have been made and used formotor vehicle body and trim parts. For example, bumpers, body panels,doors, filler panels, wheel covers, dashboards, arm rests and otherparts have been made via injection molding techniques. Additionally,with regard to vehicle exteriors, bodyside moldings, beltline moldings,roof moldings, window moldings, chin spoilers, and rocker panels, etc.are made via injection molding of PVC or other thermoplastic materials.

[0003] In order to provide a painted surface for these parts, filmlamination techniques have been successfully employed. In accordancewith these processes, a paint film laminate is insert molded with thedesired thermoplastic to fuse the film over the injection molded part.The resulting injection molded part is ready for assembly withoutsubsequent painting.

[0004] The paint film laminate used in these insert molding techniquesmay comprise a backing sheet of about 0.020″ in thickness to which paintlayers are adhered. Typically, the backing sheet comprises an extrudedthermoplastic sheet.

[0005] In such paint film laminates, a paint film comprising a castdried continuous paint coating, is provided over the backing sheet. Thepaint film may consist of a monocoat, a clear coat over a base coat, ora clear coat and a base coat with interposed print or design. The paintfilm, including base coat, clear coat and print or design, if desired,may range from about 0.5-4 mil. in thickness.

[0006] The laminated paint films are available, for example, from avariety of manufacturers. The films are typically provided in a roll,unwound and then trimmed to a proper “preformed” size and shape, readyfor insertion into the injection mold. The preform is usually placedalong the cavity side of the mold with the painted side thereof facingthe mold cavity surface. In some instances, the preform may be placedalong the core side of the mold. The mold is then clamped and thedesired molten resin is injected into the mold cavity. Heat and pressureconditions in the mold partially melt the backing sheet and a meltbonding or fusion of the injected resin and film occur. Injection moldsused for these processes are rear or edge gated so that the molten resinis directed along the backside of the film.

[0007] Although these processes provide significant advantage, they arenot without problem. For example, edge portions of the part, such as thelongitudinally extending edges of elongated strips used for bodymoldings and the like, may not be completely covered with the film.Accordingly, these edges reveal the uncovered plastic substrate andprovide an aesthetically displeasing appearance since the continuity ofthe printed surface is interrupted by the unsightly appearance of theunderlying plastic substrate.

[0008] A variety of methods have been developed to cover the edgeportions of these co-molded strips. For example, in accordance with U.S.Pat. Nos. 5,599,608 and 5,783,287 (both of common assignment herewith),the paint film is preformed prior to the co-molding step so that thelongitudinally extending edge portions thereof have reentrantdispositions relative to the remaining body of the film. Additionally,as set forth in U.S. Pat. No. 5,746,962 (of common assignment herewith),edgewise extremities of the mold cavity, referred to as “pockets,” areprovided contiguous to the mold parting line so that, upon co-molding,the desired end of the film positioned in the pocket will be superposedover the molten plastic injected into the pocket. This forms an edgeportion of the resulting plastic part wherein the film substantiallycovers the edge.

[0009] The technology reported in the above patents has proventremendously successful, especially in connection with the manufactureof deep draw or deep dimension parts. However, in the manufacture ofrelatively flatter trim parts, product reject problems have beenencountered due to shifting or rotation of the film in the mold cavityprior to injection of the molten plastic. Additionally, high pressurepinching of the film between the male and female mold platens along themold parting line also results in undesirable product rejects.

[0010] With respect to this latter problem, the high pinching force(usually on the order of about 600 tons) can result in a serrated orfeathered edge appearance of the film laminate along the edge of theplastic part thereby leading to the requirement of an additionallabor-intensive product trimming step so that the product can complywith stringent product quality standards.

SUMMARY OF THE INVENTION

[0011] Briefly, improvement in prior art techniques is provided byutilization of a specific mold cavity structure which facilitateswrapping of the paint film around the desired edge portion of theplastic part while minimizing the chance that the film will shift orrotate out of proper alignment in the mold cavity. Additionally, thecavity structure provides for a distinct physical separation of the edgeextremity of the mold cavity from the mold parting line. This featurehelps to minimize high pressure pinching of the film edge that mayotherwise occur in the high pressure nip location existing at the moldparting line.

[0012] More specifically, the mold comprises a male, core portion and afemale concavity portion. Together, the space between the core portionsurface and concavity surfaces defines a mold cavity adapted for receiptof a paint film laminate therein normally positioned with its showsurface facing the concavity. As per conventional practice, the sprueand gating are attached to the core side of the mold. Of course, therelative positioning of the film in the mold cavity and the direction ofthe plastic entry and flow into the mold cavity could be easilyswitched.

[0013] A mold parting line is defined by the mating surfaces of the maleand female mold portions. An extremity of the mold cavity is provided inone of the mold surfaces, typically in the core portion. This extremityupon completion of molding, will form an edge of the desired plasticpart. This extremity is referred to herein as a wrap around surface.

[0014] In contrast to prior art structures and methods in which the moldextremity is located along or is contiguous with the parting line of themold, the wrap around surface in accordance with the invention is offsetor spaced from the mold parting line as measured along a vectorperpendicularly oriented with respect to the plane defined by the moldparig line.

[0015] Molten plastic is inserted into the mold cavity and is directedagainst the wrap around surface and the paint film end positioned atthis extremity of the mold cavity. The paint film end will pivot alongthe wrap around surface to thereby form the desired plastic part whereinan edge portion of the plastic will be substantially covered or wrappedby overlying paint film.

[0016] The invention will be further described in conjunction with theappended drawings and following detailed description.

DRAWINGS

[0017]FIG. 1 is a sectional view of a prior art mold cavity;

[0018]FIG. 2 is a magnified sectional view of a portion of the prior artmold cavity shown in FIG. 1;

[0019]FIG. 3 is a sectional view of a preferred mold cavity inaccordance with the invention;

[0020]FIG. 4 is a magnified sectional view of a portion of the moldcavity shown in FIG. 3 shown with a co-molded paint film laminate andunderlying plastic material therein;

[0021]FIG. 4a is a magnified sectional view of a mold cavity inaccordance with another embodiment of the invention;

[0022]FIG. 5 is a magnified sectional view of a portion of a paint filmlaminate covered plastic trim part made in accordance with theinvention;

[0023]FIG. 6 is a plan view of a paint film covered plastic trim partmade in accordance with the invention; and

[0024]FIG. 7 is a transverse cross sectional view of the trim part shownin FIG. 6, taken along the lines and arrows 7-7 of FIG. 6.

DETAILED DESCRIPTION

[0025] Turning first to FIGS. 6 and 7 of the Application, there is showna trim part such as a bodyside molding member 6 made in accordance withthe invention. The trim part 6 is elongated and presents anaesthetically pleasing appearance due to the provision of the show side8 of paint film laminate over the plastic substrate 10.

[0026] As can be best seen in FIG. 7, the longitudinally extending edges12, 14 of the substrate 10 are completely covered or wrapped around atwrapped edges 18, 20, by the paint film 16. The part shown in FIGS. 6and 7 is provided in accordance with the instant co-molding process asshall be set forth hereinafter.

[0027] Turning now to FIG. 1 of the invention, there is shown a priorart mold of the type utilized to produce plastic parts. Here, the mold100 comprises a male core member 102 and cooperating female member 104.The male mold member comprises a convex core surface 106 whichcooperates with the female concave surface 108 to, therebetween, definea mold cavity 110 in which the paint film covered parts are made.

[0028] The longitudinal extending edge extremities of the mold cavityare provided as a pair of surfaces which will extend longitudinallyalong the finished, molded elongated part. Here, left hand extremity 112and right hand extremity 114 are provided. Note that both of theseextremities are contiguous with the horizontally disposed part line ofthe mold shown at 116.

[0029] With further regard to FIG. 1, sprue 118 is in communication witha source of molten plastic so that it may serve as an entry location forplastic flow into the mold cavity.

[0030] The step of co-molding itself is not new. In accordance withtraditional co-molding techniques, the paint film laminate is firstplaced in the mold cavity, typically with the show side of the paintfilm laminate contiguous to or spaced closely from the concave surface108 presented by the female portion of the mold. Then, plastic isinjected through the sprue, and fills the mold so that the resultingco-molded part consists of a plastic substrate covered by paint filmlaminate along the face and edges of the substrate.

[0031] As shown in FIG. 2, the right hand extremity 114 of the prior artmold cavity is contiguous with the parting line of the mold 116, inaccordance with prior art processes and structures.

[0032]FIG. 3 of the drawings depicts a mold cavity made in accordancewith the invention. Here, the mold 200 comprises core member 202 andcooperating female member 204. The male core surface is shown at 206with the cooperating surface of the female mold member shown at 208.Between the members 206 and 208, a mold cavity 210 in accordance withthe invention is provided. Here, the left hand and right hand edgeextremities of the mold cavity 212, 214 respectively, are off set fromthe part line 216 of the mold. That is, the edge extremities 212, 214are spaced from the part line 216 as would be measured along a vectorpositioned perpendicular to the part line 216. Instead, the edgeextremities 212, 214, as shown herein, are contiguous with the planeprovided along part line 220 of the part. Sprue 218 serves as an entrylocation for flow of injected plastic into the mold cavity.

[0033] Location of the edge extremities 212, 214, in an off set orspaced position from the part line of mold 216 has provided distinctadvantage. Especially when the desired part is a shallow one,heretofore, the paint film, when positioned in the mold cavity, tendedto shift and in some cases fell out of the mold cavity. Here, theshifting or rotation of the paint film, will be corrected by pivoting ofthe edgewise portion of the paint film against the extremities 212, 214,which are also referred to as wrap around surfaces herein. Further, inmany of the prior art processes, in which these edgewise extremities ofthe mold are located contiguous to the mold parting line, misalignedpaint film, in accordance with the prior art processes, tended to shiftinto the nip between the mold parting line, and these edges were thensubjected to excessive pressure forces and formed deleterious, featheredor serrated edges.

[0034] In accordance with the invention, the pressures encountered atthe part line of the part 220 are much less than those experienced atthe part line of the mold 216, so the tendency to form feathered orserrated edges is accordingly minimized.

[0035] Turning now to FIG. 4, there is shown a magnified sectional viewof a part in accordance with an invention shown in its position in themold, prior to opening of the mold for part ejection. The view here istaken of a co-molded part in which a paint film has been fusingly bondedby the molding process over the plastic injected into the mold. Here,the edge 14 of the part is completely wrapped around or covered by paintfilm 16 as shown at 20. The wrap around edge 214 of the male or coresurface is coplaner and contiguous with the part line 220 of the part.

[0036] Another embodiment is shown in FIG. 4a, wherein the wrap aroundsurface comprises a concavity 214 a contiguous with the part line 220 ofthe part, spaced above the part line of the mold 216 (FIG. 3).

[0037] In accordance with the invention, it is possible to provide partsof the type shown in FIG. 5 wherein an angle ∝ of less than 90 degreesis provided between vertices 300, 302. Vertex 300 represents a tangenttouching the curved surface of the part existing on the face or showside of the part, adjacent to the left hand longitudinal edge 18 of thepart 6. Vertex 302 represents the plane presented by the edge 18 of thepart. Note that the edge 18 of the part as represented by the vertex 302is straight or planar. This edge extends parallel to the longitudinalaxis 105 of the part 6 as shown in FIGS. 6 and 7. Accordingly, by use ofthe methods and mold cavity structure reported herein, the pair oflongitudinally extending edges 12 and 14 are flat (not rounded) and arecompletely wrapped or covered with paint film 18, 20.

[0038] Having described the invention in detail and by reference topreferred embodiments thereof, it will be apparent that modificationsand variations are possible without departing from the scope of theinvention defined in the appended claims.

What is claimed is:
 1. Method of making a plastic part by insert moldingof a paint film over a plastic substrate, comprising (a) providing amale mold member including a core portion and a female member having asurface defining concavity therein, said male mold member and saidfemale mold member defining a mold cavity therebetween and mating alonga generally planar parting line, said male mold member comprising atleast one wrap around surface disposed at an extremity of said moldcavity and spaced from said parting line; (b) inserting a paint filminto said mold cavity and positioning an end of said film adjacent saidwrap around surface; (c) injecting molten plastic into said mold cavityand directing said molten plastic against said wrap around surface andagainst said film end positioned adjacent said wrap around surfacewhereby said film is superposed over said molten plastic positionedadjacent said wrap around surface, thereby forming said plastic partwith an edge portion of said substrate substantially covered by saidpaint film.
 2. Method as recited in claim 1 further comprising providingsaid at least one wrap around surface along a plane generally parallelto said parting line plane.
 3. Method as recited in claim 1 comprisingproviding a pair of wrap around surfaces, each said wrap around surfacelocated along an opposite edgewise extremity of said mold cavity. 4.Method as recited in claim 1 wherein said wrap around surface is in theform of a concavity.
 5. Method as recited in claim 1 wherein said wraparound surface is substantially planar.
 6. Method as recited in claim 1wherein said wrap around surface is provided on said core portion. 7.Plastic part made by the process of claim
 1. 8. Plastic part made by theprocess of claim 3.